As service types increase, a service routing network needs to be deployed in a network to improve service quality. At present, a service function chain (SFC) technology is generally used to transmit a packet in the service routing network.
As shown in FIG. 1, a main idea of the SFC technology is that a service classifier (SCLA) classifies a packet and sends the classified packet to a service function forwarder (SFF) to which a corresponding service function (SF) entity is attached, and the SFF sends the packet to the corresponding SF entity for processing.
The packet entering the service routing network is encapsulated with a service function chain header, and the service function chain header includes information about a service function chain. The SFF sends, according to the service function chain header of the packet, the received packet to the corresponding SF entity for processing. The corresponding SF entity encapsulates processing result information of the packet into the service function chain header. However, the SF entity includes some legacy SF entities, and the legacy SF entities do not support a packet that carries a service function chain header. Therefore, how to be better compatible with a legacy SF, so as to transmit, in a network architecture in which a legacy SF exists, a packet carrying a service function chain header becomes a problem that needs to be resolved.